import time
from django import forms
from django.forms.util import ErrorDict
from django.conf import settings
from django.contrib.contenttypes.models import ContentType
from django.utils.crypto import salted_hmac, constant_time_compare
from django.utils.encoding import force_text
from django.utils.text import get_text_list
from django.utils import timezone
from django.utils.translation import ungettext, ugettext, ugettext_lazy as _
from models import UserImage


class UserImageForm(forms.Form):
    timestamp     = forms.IntegerField(widget=forms.HiddenInput)
    security_hash = forms.CharField(min_length=40, max_length=40, widget=forms.HiddenInput)
    honeypot      = forms.CharField(widget=forms.HiddenInput, required=False)
    userimage     = forms.FileField()


    def __init__(self, data=None, initial=None):
        if initial is None:
            initial = {}
        initial.update(self.generate_security_data())
        super(UserImageForm, self).__init__(data=data, initial=initial)

    def security_errors(self):
        """Return just those errors associated with security"""
        errors = ErrorDict()
        for f in ["honeypot", "timestamp", "security_hash"]:
            if f in self.errors:
                errors[f] = self.errors[f]
        return errors

    def clean_security_hash(self):
        """Check the security hash."""
        security_hash_dict = {
            'timestamp' : self.data.get("timestamp", ""),
        }
        expected_hash = self.generate_security_hash(**security_hash_dict)
        actual_hash = self.cleaned_data["security_hash"]
        if not constant_time_compare(expected_hash, actual_hash):
            raise forms.ValidationError("Security hash check failed.")
        return actual_hash

    def clean_timestamp(self):
        """Make sure the timestamp isn't too far (> 1 hours) in the past."""
        ts = self.cleaned_data["timestamp"]
        if time.time() - ts > (1 * 60 * 60):
            raise forms.ValidationError("Timestamp check failed")
        return ts

    def clean_honeypot(self):
        """Check that nothing's been entered into the honeypot."""
        value = self.cleaned_data["honeypot"]
        if value:
            raise forms.ValidationError(self.fields["honeypot"].label)
        return value

    def generate_security_data(self):
        """Generate a dict of security data for "initial" data."""
        timestamp = int(time.time())
        security_dict =   {
            'timestamp'     : str(timestamp),
            'security_hash' : self.initial_security_hash(timestamp),
        }
        return security_dict


    def initial_security_hash(self, timestamp):
        initial_security_dict = {
            'timestamp' : str(timestamp),
          }
        return self.generate_security_hash(**initial_security_dict)


    def generate_security_hash(self, timestamp):
        """
        Generate a HMAC security hash from the provided info.
        """
        info = (timestamp,)
        key_salt = "image.forms.UserImageForm"
        value = "-".join(info)
        return salted_hmac(key_salt, value).hexdigest()

